ul{
    list-style: none;
}

.box{
    width: 300px;
    height: 300px;
    background-color: orange;
    background: url('../images/小毛驴.png'); 
}

.example-enter {
  opacity: 0.01;
}

.example-enter.example-enter-active {
  opacity: 1;
  transition: opacity 500ms ease-in;
}

.example-leave {
  opacity: 1;
}

.example-leave.example-leave-active {
  opacity: 0.01;
  transition: opacity 300ms ease-in;
}
/*刚一出现时候的动画*/
.example-appear {
  opacity: 0.01;
}
.example-appear.example-appear-active {
  opacity: 1;
  transition: opacity .5s ease-in;
}